The present invention relates to fluorescence, and more specifically, to structures comprising material that fluoresces when exposed to light.
Organic fluorescent dyes have been employed in structures comprising a plate of a material that is transparent to light. The material has an organic fluorescent dye distributed within its volume. The plate has a top surface and is surrounded by edges. The top surface of the transparent plate is oriented to receive the light. Light incident on this top surface penetrates into the plate and is absorbed by the organic fluorescent dye which in turn emits longer wavelength light having a narrow wavelength distribution. The light emitted by the fluorescent dye propagates through the plate to its edges. The plate is preferably thin so as to provide a large surface area for collecting light and has narrow edges where the light emitted from the fluorescent dye exits the plate. Large amounts of light can therefore be collected and concentrated into a smaller region. One disadvantage of such organic-based structures is that they have a short lifetime, lasting typically about 1-4 years. The organic fluorescent dyes contained within the structure decompose upon extended exposure to ultraviolet (UV) light, which, for instance, is abundant in sunlight. Thus, there is a need for a structure for collecting light and converting it into high intensity narrow band illumination that is not rendered inoperative by UV light.
In one aspect of the invention, an apparatus comprises a layer of quantum dots that emits light in response to exposure to pump radiation and a waveguide which receives and guides light emitted by the layer of quantum dots.
In another aspect of the invention, a waveguide has a substantial number of quantum dots which emit light in response to pump radiation. The quantum dots are disposed in relation to the waveguide such that light emitted by the quantum dots is captured by the waveguide and guided therein.
In yet another aspect of the invention, a method of illumination comprises illuminating quantum dots disposed over a relatively large area with pumping radiation. These quantum dots are used to emit light in response to the pumping radiation. Light emitted by the quantum dots is collected and used to illuminate a relatively small surface area.